Critical fixes #1-8: wall coords, calib reset, cmd=0 guard, fence marking, loc_conf, params callback, CMake maps

- SessionMapper: fix wall line construction (0/w/h → x_min/x_max/y_min/y_max)
- session_mapper.reset() on calibration failure
- CALIBRATING state forces cmd_vel=0
- GridMap::markFenceModel() draws calibrated fence into static_cells_
- /nav_metrics now publishes loc_conf
- add_on_set_parameters_callback handles all new params
- CMake maps install guarded with EXISTS check

include/car_nav_lite/grid_map.hpp

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "car_nav_lite/types.hpp"
+#include "car_nav_lite/fence_model.hpp"
 #include <string>
 #include <array>
 
@@ -54,6 +55,7 @@ public:
     // ── Pre-built obstacle marks ───────────────────────
     void markCircle(double wx, double wy, double radius, uint8_t value = 255);
     void markCone(double wx, double wy, double radius, uint8_t value = 255);
+    void markFenceModel(const FenceModel& fence, double thickness = 0.04);
     void markRect(double x1, double y1, double x2, double y2, uint8_t value = 255);
 
     // ── Getters ────────────────────────────────────────

include/car_nav_lite/session_mapper.hpp

@@ -20,6 +20,7 @@ public:
                double expected_size = 5.0, double size_tol = 0.35,
                double ransac_thresh = 0.04);
 
+    void reset() { points_world_.clear(); scan_count_ = 0; }
     int scanCount() const { return scan_count_; }
     const std::vector<Eigen::Vector2d>& points() const { return points_world_; }